This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Intervertebral disc degeneration is a common and sometimes debilitating condition affecting a significant percentage of the population. The earliest stage of disc degeneration involves the breakdown of proteoglycans in the nucleus pulposus region of the disc. The current diagnostic method for disc degeneration relies on T2 -weighted proton MRI, which is not sensitive to proteoglycan breakdown. T1[unreadable] MRI has been shown to be sensitive to the interaction between large macromolecules like the proteoglycan and bulk water, thus it is potentially sensitive to the proteoglycan concentration in IVD. Sodium MRI has been shown to be an accurate measurement of proteoglycan content, since Na+ cations are attracted by the fixed-charge density of the proteoglcyan molecules. The purpose of this study is to demonstrate T1[unreadable] as a measurement of disc PG content, by correlating T1[unreadable] relaxation time constants with [Na+] using self-coregistered proton T1[unreadable] and sodium MR images of ex vivo bovine disc samples. Since sodium MRI has limited application in clinical settings due to the inherent low SNR and hardware requirement, T1[unreadable] MRI may serve as a more suitable approach to non-invasive assessment of disc proteoglycan content in vivo.